Jet Propulsion?


#85

Hi Virus,

Awesome job on the efoil. I appreciate the carbon work and your attention to detail. Its impressive.
Not only that but it works. :slight_smile: What speeds are you hitting? I’m looking at direct drive and wondering if you have shared your impeller design? If you’d rather not, how did you come up with a good working design? Trial and error? I have a good idea for most of the other items(thanks for the vids)…just wondering about impeller
thanks!
MIke


#86

hey, where did you get the 96mm impeller?


#87

Hey MikeL,
My quick thoughts and experience:
I like direct drive for sure over reduction gear. less everything literally…
Less costs, less parts, less maintenance, less thrust so be sure to use larger board and larger foil

It does draw more current as smaller and faster spinning props are not as efficient as larger props but I don’t mind giving up a few minutes of ride time if I don’t have issues to deal with and its safer along with many other benefits.

We are still tweaking impellers and Ill get back to you on that.


#88

Ok thanks VeFoil. I’ve decided to take @PowerGlider 's and @Mat approach. Its direct drive and seems like the simplest solution. I just received the 100kV motor. Its fun to see the parts come in. ha Now looking for bearing and epoxy. There seems to be a ton of epoxies you can use to waterproof a motor…just looking for the right one. Should be high viscosity to get in all the windings.
Still really want to see how you make out. I’m sure your jet will work well. Your stuff looks pro(and safe)
I’ve watched yours, @pacificmeister and @virus vids and learned a ton. This forum is wealth of knowledge and much appreciated. I doubt I would have done this otherwise.


#89

I mean low viscosity


#90

Cool looking forward to seeing your progress!!! @MikeL
Low viscosity helps a lot, but I would advise not to use an epoxy-based adhesive. Rather a polyurethane based adhesive which is more flexible. The windings will generate heat and there will be a temperature difference between the windings, adhesives, casing and water. The materials will expand differently due to there properties. Which will result in high stress concentrations (in the adhesive) with may led to cracking and ultimately water ingress. There are also a lot of vibrations which does not help either. So, I strongly advise an adhesive with has some flex, and can resist saltwater.


#91

Hi Hiorth…I forgot to mention you. I must have read your build many times. I want to try building a battery pack after I get this going like you did. nice job! For now I’ll stick to the easy solution(lipo)
Thanks for the feedback. There are actually many flexible epoxies out there but good call on the urethane. I’ll look for something thermally conductive.
Your board looks great too…its what I want to do.
cheers


#92

I’m using the same epoxy as i use to make surfboard… it’s quite flexible in think coats.
Don’t bother with thermal conductivity, i think someone from the forum checked and you won’t get any useful improvement. Instead, focus on keeping it thin…
I think i applied 2 or 3 coats with a paintbrush and that’s it. I can say for sure it survived well to trial session in half salty water… not sure for long term yet :slight_smile:


#93

Ok thanks
I found these two companies. I’ll inquire to see…
http://www.epicresins.com/ElectronicsPotting/MotorsStators


Sounds like the Corrosion X worked for you. I just bought some.
I’ll also really make sure the motor connections are protected.


#94

Corrosion X need to be applied regularly (after each use)
and protect the bearing, and exposed metal part… not sure it would do much to waterproof electrical connection… i trust adhesive line shrink tubing better for that … and/or liquid tape


#95

I was thinking this for the wires coming out of the motor


then shrink tube the connection(with adhesive),
and switch to these bearings


#96

ceramic will be great for corrsion BUT:

  • they won’t be as tolerant with axial load (metal ones, can take more, deep groove ones even more.)
    Axial load is not negligible if you don’t add a dedicated axial bearing…
  • they’re expensive and harder to find…

#97

You say “the board volume= your weigh + 30l

So a rider who is 100kg you think should be riding 130L board? ?


#98

And the weight of the setup ( for beginners)


#99

yes, that is 85% of us :slight_smile: